1. Field of the Invention
The invention relates to a drying device for drying bulk material. The drying device comprises at least one storage container for the bulk material and a heating device with which the drying air for drying the bulk material is heated, wherein the drying air flows in a drying air conduit to the storage container.
2. Description of the Related Art
It is known to dry any type of bulk material in a storage container. For this purpose, a heated medium, preferably air, with a minimal water contents is guided through the bulk material in order to take up the moisture of the bulk material and to guide it via a conduit system out of the storage container to a dehumidification system. In this dehumidification system, the moisture is removed from the drying medium. The dehumidification is carried out by means of drying air dryers or other suitable dehumidification devices.
It is also known in the drying technology to preheat air for drying bulk material by means of heating devices and to supply the drying air via insulated conduits to the storage containers. When the drying devices have several storage containers, each storage container has correlated therewith a heating device in order to bring the supplied preheated air to the required temperature before the air enters the respective storage container.
As soon as the drying air dryer (drying unit) is saturated with moisture, it is regenerated. For this purpose, at least one additional heating device is provided with which regenerating air is heated to correspondingly high temperatures in order to remove the moisture from the drying medium.
These drying devices are of a complex construction and operate with a great energy expenditure.
It is an object of the present invention to configure the drying device of the aforementioned kind such that it can be operated with minimal energy expenditure while having a constructively simple configuration.
In accordance with the present invention, this is achieved in that a mixing valve is provided upstream of the storage container in the drying air conduit with which the temperature of the drying air can be adjusted before the drying air enters the storage container. This is furthermore achieved according to another embodiment in that a single heating device is used for heating the drying air and for regenerating the at least one drying medium unit.
The drying device according to the invention has only a single heating device for supplying one or more storage containers with heated drying air. By means of the mixing valve, the temperature of the drying air can be adjusted to the desired drying temperature before the drying air enters the storage container. As a result of the configuration according to the invention, the heating device can also be economically employed for small drying devices with many storage containers based on the selection of the energy carrier, for example, gas. The heating device is sized for the total output of the drying device and can thus be realized in a cost-efficient way. Accordingly, the use of expensive electricity for operating the heating device is no longer needed.
According to the above mentioned further embodiment, only a single heating device is used for the drying air as well as for the regenerating process of the drying medium unit, and the single heating device can be operated with a cost-efficient energy carrier, for example, gas. The use of a single heating device in the drying device according to the invention thus makes it possible to employ an economical heating technology for small drying devices.